1.3 Ganciclovir (GCV) and Valganciclovir (VGC) GCV was an antiviral agent had been used in treatment or prophylaxis of cytomegalovirus infection in solid organ transplantation recipients or bone marrow transplantation (14). GCV is a synthetic analogue of 2'-deoxy-guanosine and can be phosphorylated to ganciclovir triphosphate, a competitive inhibitor of deoxyguanosine triphosphate (dGTP) incorporation into DNA and preferentially inhibits viral DNA polymerases more than cellular DNA polymerases, by viral and cell kinase. In addition, ganciclovir triphosphate serves as a poor substrate for chain elongation, thereby disrupting viral DNA synthesis by a second route (15).